State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047, China.
State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047, China.
Food Chem. 2022 Dec 1;396:133662. doi: 10.1016/j.foodchem.2022.133662. Epub 2022 Jul 9.
It is still unclear how pH affects the inhibitory effects of phenolic acids and flavonoids on polyphenol oxidase (PPO). In this study, 4-hydroxycinnamic acid and naringenin were selected to investigate their interactions with PPO from pH 6.8 to 5.0. Results showed that acidic pH could enhance the inhibitory effect of inhibitors and a greater enhancement effect was observed in 4-hydroxycinnamic acid. Fluorescence emission spectra indicated that 4-hydroxycinnamic acid and naringenin interacted with PPO and quenched its intrinsic fluorescence, which was also enhanced by acidic pH. Circular dichroism suggested that 4-hydroxycinnamic acid and naringenin could reversibly bind to PPO molecules and transform α-helix into β-sheet. Molecular docking results revealed that 4-hydroxycinnamic acid and naringenin interacted with PPO through hydrogen bond and hydrophobic interaction, and more interactions were observed near the carboxyl group. These results indicated that acidic pH could significantly enhance the inhibitory effect of phenolic acid on PPO.
目前尚不清楚 pH 值如何影响酚酸和类黄酮对多酚氧化酶（PPO）的抑制作用。本研究选择 4-羟基肉桂酸和柚皮素，从 pH 6.8 到 5.0 来研究它们与 PPO 的相互作用。结果表明，酸性 pH 值可以增强抑制剂的抑制作用，而 4-羟基肉桂酸的增强效果更为明显。荧光发射光谱表明，4-羟基肉桂酸和柚皮素与 PPO 相互作用并猝灭其内源荧光，酸性 pH 值也增强了这种猝灭作用。圆二色性表明，4-羟基肉桂酸和柚皮素可以可逆地与 PPO 分子结合，并将α-螺旋转化为β-折叠。分子对接结果表明，4-羟基肉桂酸和柚皮素通过氢键和疏水相互作用与 PPO 相互作用，在靠近羧基的地方观察到更多的相互作用。这些结果表明，酸性 pH 值可以显著增强酚酸对 PPO 的抑制作用。
